3-Mercapto-5-amino-(1H)-1,2,4-triazole is known to be useful as a component of heat-developable, image-pattern, recording compositions as demonstrated by Hirabayashi et al. in U.S. Pat. No. 4,543,309. It has also found use in preparing stabilizers for photographic emulsions as taught by Merrifield et al. in British Patent No. 1,232,838. More recently, 3-mercapto-5-amino-(1H)-1,2,4-triazole has been disclosed as an intermediate for the manufacture of herbicidal compounds in European Patent Application No. 142,152.
Prior art methods of preparing 3-mercapto-5-amino-(1H)-1,2,4-triazole have generally involved condensation and/or cyclization reactions. For example, British Patent No. 1,232,838 describes the condensation of a salt of aminoguanidine with carbon disulfide to produce guanidinodithiocarbamic acid and the subsequent ring closure of this intermediate with boiling alkali. U.S. Pat. No. 4,543,309 describes the cyclization of N-guanidinothiourea hydrochloride with refluxing aqueous caustic Godfrey et al., in J. Chem. Soc., 3437 (1960), describe the condensation of isothiocyanic esters with aminoguanidine to form (amino)amidinothioureas followed by the acidic hydrolysis and cyclization of the hydrazones thereof. Polish Patent No. 126,718 describes the cyclization of H.sub.2 NC(S)NHNHC(S)NH.sub.2. Typical yields for the above preparations of 3-mercapto-5-amino-(1H)-1,2,4-triazole range from about 40 to about 80 percent.